I report estimates of long-term precision and accuracy of interstation vectors using the Global Positioning System (GPS). Precision is estimated from three experiments conducted in central Calfiornia over a period of 1.2 years. Horizontal precision is 3 to 8 mm for baseline vectors between 100 and 450 km in length, and the vertical precision ranges from 11 to 33 mm. Accuracy is assessed by comparing VLBI estimates with results from 6 GPS experiments conducted at Mojave and Palos Verdes over a period of 2.2 years. Rates for all vector components agree with VLBI within one standard deviation. ¿American Geophysical Union 1990